Process of treating metal



Feb. 22, 1938.

J. O. BETTERTON ET AL PROCESS OF TREATING METAL original Filed Aug. 17,1933 INVENTORS Jesse 05d/Wlan BYE/iz' 1i Medef] MOM/MS Patented Feb. 22,i938 OFFICE PROCESS F TREATING METAL .lesse 0. Betterton and Y tuchen,N. J., assignors and Refining Company a. Lenssen. M- to erican SmeltingNew York, N. Y., a oorporation or New Jersey Application August 17,1933, Serial No. 685,586

newed August 28, 1937 Cla.

This invention relates to an improved process of treating metals to eectthe removal therefrom of contaminating metal values.

The invention provides a process for treating 5 molten metal at lowtemperatures by which contaminating metals are readily and effectivelyremoved without the formation of excessively large amounts of complexslags or dresses.

Among other features, the invention contemplates the establishment andmaintenance of a liquid' two phase equilibrium system comprising themolten metal undergoing treatment and a slag which is uid at theoperating temperatures employed and also non-reactive with respect bothto the metal treated and reagents, if any, used.

It is, of course, well known that as a general rule the degree ofsolubility of one metal in another varies with the temperature and thatfact is commonly taken into consideration in practising ordinaryliquidation separations. Again, it is common practise to removeimpurites from metals by incorporating suitable reagents therein whichwill selectively react with the impurities and permit their accumulationand removal .as

drosses. However, these processes or combinations thereof as generallypractised usually have some'inherent disadvantages among which may bementioned the formation of large or excessive quantities of dross, thediculties encountered in treating the dross arising from both the largequantity thereof and its physical and chemical composition, theexcessive oxidation of the metal and the loss of eiciency due either tothe chemi cal conversion of relatively large amounts of the metaltreated to undesired compounds or its mechanical entrapment in theimpurity being removed.

The foregoing and other disadvantages are overcome and new and usefulresults obtained 40 by employing a two phase equilibrium system, in

accordance with the present invention' In geng eral, the improvedprocess may be practised by l covering a molten oath oi the metal to bereiined with a suitable slag, that is, one which is chemically inertwith reference both to the metal being rened and the contaminants beingremoved therefrom and which is and remains duid at the operatingtemperature employed. By agitating the bath, equilibrium is establishedand maintained between the different phases of the system. 1n ease theequilibrium value for a particular separation is not sufciently low,suitable reagents may be employed to lower such. value as will behereinafter described.

The drawing accompanying the specication is a flow sheet illustratingthe process ci the invention.

In order to more fully illustrate the many novel features and advantagesof the invention several specic examples of the process as applied to 5decopperizing lead are given, although it is to be understood that theinvention is not limited thereby as it may be utilized in conductingother refining operations, such as, for example, the desilverization oflead.

Example 1 In this instance impure blast furnace lead was meltedV down ina cast iron kettle, the dross skimmed and. the bath sampled. The totalweight of the bath was 188.5 lbs. and was shown by analysis to contain0.90% copper, 0.31% arsenic, 1.83% antimony, and 392 oz./ton dor. At atemperature of 850 F., a slag comprising 0.44 lb. of zinc chloride and0.15 lb. oi sodium chloride wasadded to the surface of the bath andallowed to melt. The bath was then agitated by an ordinary mixingmachine beginning at a temperature of 725 F. and continued until thetemperature had fallen to 600 F. At this stage a preheated hand operatedpress was placed in the kettle and the metallic mushy liquate intermixedwith the chloride slag was skimmed into the press. The bath was pressedclean at 595 F. and the pressed dross weighing only 6.25 ibs. was foundto analyze 25.3% copper. .an analysis oi the final bath which weighed'i822 lbs. showed 0.06% copper, 0.08% arsenic, 1.61% antimony and 392.0ca /ton of dor.

it will l noted that in Example 1 the copper content was reduced to0.06%, which figure represents the approximate equilibrium value iorthat system. in order, then, to lower that value and further decreasethe copper content in acn cordance with the invention, the 182.2 lbs. oflead were treated as follows: the bath wasv reheated to 660 F; and 0.22lb. of zinc chloride and 0.08 lb. of sodium chloride added and allowedto melt at 640 F. At this stage, 0.360 lb. of zinc dust wereincorporated in the bath, after which the mushy drow was pressed as inExample l. The pressed dross weighed 0.9 lb. and analyzed 6.7% copperwhile the bath weighed 181.7 lbs. and contained 0.03% copper, 0.08%arsenic, 1.67% antimony and 386.5 oz./ton oi dor. l

Example 3 In this instance, a bath of copper-bearing lead weighing 153.7lbs. after melting down and shim-n copper.

Example 4 One hundred, forty-four and eighth-tenths lbs. of lead weremelted in a small cast iron kettle and 1.1 lbs. of dross formed duringthe melting down operation were skimmed at a temperature of 660y F. Byanalysis, the bath was found to contain 0.115% copper. Powdered sulfurto the f amount of 0.175 lb. was added to the bath at a temperature of630 F. and thoroughly incorporated therein. 'Ihis operation wasperformed in 22 minutes, at which time the dross weighing 17.5 lbs. or12.08% by weight of the original lead treated was removed from the bathAat a temperature of 660 F. The molten lead bath was then sampled andfound to contain 0.06% copper. At this stage, a slag comprising 1.3 lbs.of zinc chloride and 0.3 lb. of sodium chloride was added to the surfaceof the bath and allowed to completely melt at 650 F. 'I'he 17.5 lbs. ofmushy dross were returned to the bath, the contents of the kettle mixedby hand for a few minutes and the slag skimmed from the bath. The grossweight of the slag was only 3.5 lbs. or a net weight of 1.9 lbs.,equivalent to 1.31% by weight of the lead originally treated. The bathanalyzed 0.06% copper.

` Example5 One hundred fifty-eight and one-half lbs. of copper-bearinglead were melted in a kettle and the dross formed during the meltingoperation (1.1 lbs.) removed. By analysis the bath contained 0.12%copper. After adding a slag comprising 0.66 lb. of zinc chloride and0.25 lb. of sodium chloride, sulfur to the amount of 0.66 lb. wasincorporated in the bath at a temperature of 630 F. The slag, weighing2.3 lbs., was skimmed from the surface of the bath and a sample of thebath takenl which analyzed 0.069% copper. At this stage, a second slagcomprising 0.1 lb. of zinc chloride and 0.2 lb. of sodium chloride wasadded to the surface of the bath. 'I'hereafter, 0.32 lb. of powderedzinc was incorporated in the molten lead and the temperature lowered toa point approaching the freezing point of lead. The molten metal wasthen tapped from the kettle and found to contain only 0.012% copper and0.06% zinc.

From the several preceding specific examples it will readily beappreciated that new and improved results are obtained when metals aretreated in accordance with the two liquid phase process of the presentinvention. The ease with which contaminants in metal may be reduced totheir solubility limits at the temperature employed without theproduction of large amounts oi' dross or recourse to any reagents isclearly exemplified by Example l. Examples 2 and 3, among otherfeatures, illustrate how the amount of a contaminant may readily bereduced simply by employing a reagent which will lower the equilibriumvalue. The marked reduction in dross produced by employing theequilibrium system in combination with areagent is amply brought out inExample 4, while Example 5 illustrates the consecutive use of reagentswhich impart different equilibrium values to a given two phase liquidsystem. ,f-

It is believed that the improved results obtained by the invention maybe in a large part explained on the theory that providing a suitablefluid slag on the molten metal optimum conditions of equilibrium betweenthe bath-and slag with relation to the solubility of the contaminantbeing removed are at all times maintained. Instead of forming a soliddross upon the surface of the bath, the contaminant is maintained in aliquid state and the metal which ordinarily is enmeshed in the dross isallowed to reenter the bath while at the same time the contaminant beingin amounts in excess of the solubility of same in the bath at thetemperature employed remains in the liquid slag. Hence, it follows thatwhile a vmixture of zinc chloride and sodiumY chloride has beenspecifically mentioned by way of illustration, any slag, which is fluidat the temperatures employed and which will not react with the metal orreagents, if any, used, may be utilized. It is, of course, obvious thatthe slag will also serve the secondary purpose of preventing oxidationof the bath and reagents. Y

It is obvious that in addition to decreasing the amount of drosslformed, the invention facilitates the handling and processing of theslag containing the contaminants removed from the metal both from thestandpoints of quantity and physical composition. For example, slagsobtained by decopperizing lead may be leached with water to remove thesoluble constituents therefrom and the4 residue smelted to produce aconcentrated copper matte which is readily processed for the recovery ofcopper.

While certain novel features of the invention v have been disclosed andare pointed out in the annexed claims, it will be understood thatvarious omissions, substitutions and changes may be made by thoseskilled in the art without departing from the spirit of the invention.

What is claimed is: A

1. In the process of removing copper from lead by incorporating adecopperizing reagent in the molten lead whereby copper is concentratedasa dross, the improvement which comprises conducting the operation inthe presence of a uid slag comprising a mixture of"zinc chloride andsodium chloride thereby concentrating the copper in a combined slag anddross of small weight.

2. A process of reflning copper-containing lead, which comprises formingAa molten bath of the lead, producing on they said bath a molten slaglayer comprising zinc chloride and sodium chloride, the slag layerremaining fluid at the temperature of operation and being substantiallyinert with respect to the lead in the bath, produc- 1 o temperature ofthe bath and beingsubstantially 1 inert with respect to the lead in thebath, liqu'ating the bath to produce a dross o; the copper contained inthe lead, and agitating the bath and slag to concentrate the dross inthe slag, thereby establishing conditions of equilibrium between thebath and slag, the said slag being adapted to retain the dross whilereturning to the bath the lead which was entrapped in the dross.

4. A process of refining copper-containing lead, which comprises forminga molten bath of the lead, producing on the said bath a molten slaglayer comprising zinc chloride and sodium chloride, the slag layerremaining fluid at the ternperature of operation and being substantiallyinert with respect to the lead in the bath, adding to the bath a reagentfor the copper adapted to produce a separation of the copper from thebath as a dross, and agitating the bath and slag toconcentrate the drossin the slag, thereby establishing conditions of equilibrium between thebath and slag, the said slag being adapted to retain the dross whilereturning to the bath the lead which was entrapped in the dross.

5. The process for rening lead by liquation with production of a minimumamount of dross which comprises forming a molten bath of the lead to beliquated, establishing on the bath a fluid, salt slag which ischemically non-reactive with respect to lead and which will retain itsuidity throughout the liquating temperature range, bringing the bath andslag into equilibrium with respect to the impurities to be removed bymixing the bath and slag while simultaneously cooling same therebyconcentrating impurities in the slag with minimum production of drossand effecting a separation between the refined lead and the slag.

JESSE O. BETTERTON. YURII E. LEBEDEFF.

